1. Field of the Invention
The present invention relates to a mobile robot, and more particularly, to a method and apparatus for detecting a position of a mobile robot.
2. Description of the Background Art
In general, a mobile robot is a device for automatically cleaning an area by sucking dusts or foreign materials from the floor while moving along the wall of a room (i.e., a living room, the inner room, etc.) of a house even without manipulation of a user.
The robot cleaner discriminates a distance between itself and an obstacle such as an article of furniture, official supplies and a wall installed in a cleaning area through a distance sensor, and selectively drives a motor for driving its left wheel and a motor for driving its right wheel depending on the discriminated distance, whereby the robot cleaner cleans the cleaning area by turning its direction. Herein, the robot cleaner performs a cleaning operation by traveling the cleaning area through map information stored in an internal storing unit.
A mapping operation for generating the map information will now be described.
First, the robot cleaner calculates a distance between itself and a charging unit and its direction by moving along a side surface of an operation space (i.e., a wall side of a living of a house), and scans the operation space by judging its position on the basis of the calculated distance value and the direction value. At this time, the robot cleaner detects its current position by using an encoder installed at its own wheel.
The robot cleaner judges whether there is an obstacle between itself and the charging unit, and if there is no obstacle, it scans the operation space by transmitting to and receiving from the charging unit. If, however, there is an obstacle between the robot cleaner and the charging unit, the robot cleaner scans another operation space, and then, when the obstacle disappears, the robot cleaner scans the operation space without the obstacle while transmitting to and receiving the charging unit.
However, the method for detecting a position of the robot cleaner by using the encoder has a problem that an error occurs due to a sliding of the wheel or an idle rotation because the current position of the robot cleaner is searched by using the encoder installed at the wheel.
Meanwhile, in case of the method for detecting a position of the robot cleaner in accordance with another conventional art, several stickers or reflection plates having the same shape are attached at predetermined intervals at an operation region, so that the robot cleaner can recognize the sticker or the reflection plate by using a CCD camera and correct an error generated due to sliding or idle rotation of its wheel, thereby recognizing a distance between itself and the charging unit.
However, this method has a problem that if illumination brightness of the cleaning operation region changes or an object having a shape similar to the sticker or the reflection plate is recognized, the distance error is accumulated.
The techniques on the robot cleaner in accordance with the conventional art are also disclosed in U.S. Pat. Nos. 5,440,216 and ′5,646,494.